announcer ] it's time for medicare open enrollment. are you ready? time to compare plans and see what's new. you don't have to make changes, but it's good to look. maybe you can find better coverage, save money, or both. and check out the preventive benefits you get after the health care law. ♪ medicare open enrollment. now's the time. visit medicare.gov or call 1-800-medicare. ♪ >>> i mentioned the navy, for example, and we have fewer ships than we did in 1916. well governor, we also have fewer horses and bayonets. >> that moment from the foreign policy debate got me thinking. and it led to our question of the week. during which war did the u.s. execute its last horse cavalry charge? was it, a, the civil war? b, the spanish-american war? c, world war i? or d, world war ii? stay tuned, and we'll tell you the correct answer. go to cnn.com/fareed for more of the "gps challenge" and lots of insight and analysis. you can also follow us on twitter and facebook, also remember if you miss a show, go to itunes. you can get the audio podcast for free, or you can buy the video version. itunes.com